High-tech buoys fitted with video and acoustic equipment, manufactured by Australian company Zylotech, have been purchased by the NSW government to protect a Japanese midget submarine recently discovered off the coast of Sydney.
A 500 metre protection zone was established around the sunken World War II midget M24 submarine after it was found by divers last November, 64 years after it disappeared following a Japanese attack on Sydney Harbour.

The NSW government now has purchased Zylotech's SeaWATCH Long Life Camera Sonobuoy to police the heritage site.

The sonobuoy contains acoustic and video surveillance technology to monitor and alert authorities of any incursion into the area.

In a statement to the Australian Stock Exchange, Zylotech chief executive officer Nicholas Sikiotis said the exposure the product would gain through the deal could be "pivotal" to securing other maritime surveillance work, such as on oil and gas platforms.

"With the SeaWATCH remote telemetry buoys, Zylotech is able to offer remote offshore multi-sensor platforms as well as seamless integration with land-based camera and vessel monitoring systems, such as AIS, allowing operators to access remote information from a distributed buoy/camera network," Mr Sikiotis said.

"This reference site could be pivotal in gaining further access to a wide range of maritime surveillance and marine research applications, including oil and gas platforms, aquaculture facilities, environmental monitoring, marine mammal research, defence and critical infrastructure facilities."

The M24 disappeared after three Japanese subs entered Sydney Harbour on May 1, 1942, in an attack that killed 19 Australian and two English sailors aboard the barracks ship HMAS Kuttabul.

The fate of the other two subs was always known, one of them blown up by her crew after it became entangled in a defensive boom net, and the other sunk by a depth charge.

But the M24 escaped, and its whereabouts had remained a mystery until a group of divers found the submarine off Sydney's northern beaches.

The wreck now is protected under the federal Historic Shipwrecks Act and NSW Heritage Act.